Insulated wire



Oct. 30, 1928. 1,689,311

E. B. WHEELER INSULATED WIRE Filed Oct. 9, 1924 by A 27} Patented Oct. 30, 1928.

UNITED STATES PATENT OFFICE.

EDMUND 3. WHEELER, 0] YORK, N. Y., 'ASSIGNOR '10 WESTERN ELECTRIC COM- PANY, INCORPORATED, 0] NEW YORK, N. Y., A CORPORATION OF NEW YORK.

msuna'rnn WIRE.

Application filed October 9, 1924. Serial No. 742,498. a

This invention relates to electrically insulated wire" and particularly to soscalled fiameroof electrically insulated wire.

An 0 ject of the invention is to provide a covering for a wire which shall be substantially flame-proof as Well as an eflicient 1nsulator or non-conductor of electricity.

A feature of the invention is a wire having a coating thereover comprising selenium and cellulose acetate.

A further feature is a wire having an insulating covering and a coat-ing thereover containing selenium and cellulose acetate.

A further feature is a wire having an insulating covering, a coating COIIIPIlSlIlg selenium and cellulose acetate over the insulating covering, and an exterior textile covering.

A further feature is a wire having'an msulating covering, a coating of finely-divlded selenium and cellulose acetate over the insulating covering, and an exterior covering of flame-proofed cotton.

The single figure of the drawing shows an insulated wire embodying one form of the invention.

Referring to the figure, the insulated wire comprises a core 1 of electrically-conducting material, a coating 2 of insulating material applied over the core 0 flame-proof material comprising finelydivided selenium and cellulose acetate over the insulated coverin 2, and an exterior textile covering 4., suc as cotton or flameproofed cotton, applied over the flame-proof coating 3.

One way of producing the flameroof insulated wire embodying the invention is to pass a wire of electrically conducting material which may have an insulation covering, such as rubber, rubber compoundsor enamel, through a bath containing a solution of cellulose acetate lacquer having finely-divided selenium in suspension therein, the solution being of the proper consistency to give the requ1red thickness of coating. The cellulose acetate lacquer may comprise cellulose acetate dissolved in a suitable solvent, such as acetone. The wire may be drawn through the solution in any suitable manner, but-preferably should be drawn out of the solution in a vertical direction so as to obtain a coatin of uniform thickness around the wire. en

1 a second coatin 3 the wire is withdrawn from the solution,' after a short interval of drying in air, which may be heated, the lacquer solvent will evaporate and a uniform coating 3 of dried or partlally dried-mixture comprising finely-divided selenium and cellulose acetate will be obtained on theinsulated wire.

A very small amount of the finely-divided 0 selenium mixed with the cellulose acetate lacquer will give ver effective flame-proofing. \Yhen heat is app ied to the wire, the selemum powder, apparently, acts as a rapid dea oxidizer, thus maintaining the insulated conductor beneath in an inert atmosphere and making it resistant to flame. Cellulose acetate has several properties which make its use esgeclally advantageous on insulated wire. ec'ause of 1ts ood adhesive qualities, the cellulose acetate acquer makes a satisfactory bmding medium for the finely-divided selemum and gives a coating which will have sufficient flexibility and adherence to permit reeling and considerable handling; the cellulose acetate lacquer dries quickly which is a manufacturing advantage; in itself, cellulose acetate is an effective insulator and non-conductor of electricity; it is not hygroscopic and therefore the insulation re- 30 sistance remains high under varying atmospheric conditions, and the covering also provides considerable water-proofing; and it is relatively non-combustible and therefore gives-a ditional flame-proofing other than 35 that obtained from the finely-divided selenium.

The flame-proofing coating comprising finely-divided selenium and cellulose acetate may be further protected from abrasion by applying an outer textile covering or serving 4,

referably of cotton or cotton braid, over it y rocesses well known in the art, and an addltional flame-proof and water-proof protection may be obtained by impregnating the textile fabric with any suitable flame-proofing material, for example with sodium-magnesium borate. v i e If desired, the textile covering 4 may be applied before the coating containing cellulose 10o acetate has dried, so that the coatin in its liquid or partially set condition is ta on up to some extent by the covering thus improv-- ing the adherence between the covering and the insulated conductor. In either case, the finely-divided selenium and the cellulose acetate are 'ven further protection from abrasion by t c covering, practically continuous coating of the flame-proof material is thus maintained over the insulation coating.

The wire produced as above described is found to be an efiicient flame-proof conductor which may be used in any situation where fiame-proofin is necessary.

What is clalmed is 1. Means for flame-proofing a conductor comprising a coating of finely-divided selenium and cellulose acetate.

2. An insulated wire comprising a core of electrically conducting material having a coating of insulating material, and a second coating comprising selenium and cellulose over said first mentioned coating, and a textile covering over said second coating.

4:. An insulated wire comprising a core of electrically conducting material having a coating of insulating material thereover, a second coating comprising selenium powder 3 and cellulose acetate applied over said first mentioned coating, and a cotton covering impregnated with flame-proofing material applied over said second coating.

5. A wire having an electrical insulation of 3 rubber, a flame-proof insulation of powdered selenium and cellulose acetate applied over the rubber, and a mechanical insulation of closely woven cotton applied over said flameinsulation.

6. A flame-proof insulation for electrical conductors, comprising a coating of cellulose acetate having finely divided selenium suspended therein.

-In witness whereof, I hereunto subscribe 4 my name this 29th day of September A. D.,

EDMUND B. WHEELER. 

